1. Field of the Invention
The present invention relates to an apparatus and a method for synchronizing picture signals without using a delay circuit.
2. Description of Related Art
In a still video apparatus, such as a still video camera, color signals R, G and B having luminance signals Y obtained by a color image pickup device are separated, for example, into the luminance signals Y and line-sequential differential color signals LSC (R-Y, B-Y) for reproduction. The luminance signals Y and the line-sequential differential color signals LSC are FM-modulated by different carrier frequencies and are subject to a multiple recording together with a predetermined synchronizing signal and an ID signal, etc. Upon reproduction of the recorded signals, the luminance signals and the line-sequential differential color signals LSC are separated by a low bandpass filter and a high bandpass filter and are subject to predetermined operations including a demodulation to be outputted.
The line-sequential differential color signal LSC includes color difference signals R-Y and B-Y that are recorded in alternate horizontal scanning periods (1H). Accordingly, it is necessary to synchronize the color difference signals R-Y and B-Y with the luminance signals so as to reproduce a picture on a monitor, etc.
To this end, memories (RAM 97 and 98) are provided in a conventional reproducing circuit to temporarily store the line-sequential differential color signals LSC, as shown in FIG. 12. One of the color difference signals is delayed by a delay circuit 93 to synchronize the color difference signals R-Y and B-Y which are then written in the respective RAM's. Namely, whether the line-sequential differential color signal LSC which has been demodulated by a color signal FM demodulation circuit 91 is the color signal R-Y or the color signal B-Y is judged by an judging circuit 92. If the line-sequential differential color signal LSC is the color signal B-Y, the latter is delayed by the 1H delay circuit 93 by a period of time corresponding to 1H (i.e., one horizontal scanning period), so that the analog color signal B-Y is converted to a digital signal by an A/D converter 95 (or 96) through a switch circuit 94, in synchronization with the color difference signal R-Y which is outputted at a period of time 1H after the color difference signal B-Y and converted by an A/D converter 96 (or 95). The digital color difference signals R-Y and B-Y are simultaneously written in the R-Y signal memory 97 and the B-Y signal memory 98 at the same addresses thereof, respectively. The color difference signals R-Y and B-Y stored at the same addresses of the memories 97 and 98 are simultaneously read therefrom.
The luminance signal Y and the color signal C have different modulation frequencies (i.e., different carrier frequencies). For example, the modulation frequency of the luminance signal Y is higher than the modulation frequency of the color signal C. Accordingly, when these signals are separated by the color filters, the color signal C is delayed with respect to the luminance signal Y. Consequently, upon reproducing a picture onto a monitor or the like, it is necessary to compensate for the delay so that the color signal C and the luminance signal Y will be simultaneously output (i.e., so that the color signal C and the luminance signal Y will be synchronized).
To this end, in a known synchronization circuit, a delay line 101 is provided in the reproduction circuit of the luminance signal Y to delay the transmission of the luminance signal Y and thereby synchronize the luminance signal Y and the color signal C, as can be seen in FIG. 13.
Furthermore, in a known synchronization circuit having memories for storing the color difference signal C and the luminance signal Y therein, as shown in FIG. 14, the luminance signal Y is stored in the luminance signal memory 103Y and the color difference signal C is stored in the color signal memory 103C. When the luminance signals and the color signals, together constituting a single picture plane, are stored, the luminance signals and the color signals corresponding to the same horizontal line and same picture element (i.e., pixel) are successively read from the respective memories 103Y and 103C to synchronize the luminance signals and the color signals. The conventional memory controller 105 which controls the writing and reading operations of the signals in and from the memories includes a Y-address counter 105Y and a C-address counter 105C to control the addresses of the Y memory 103Y and the C memory 103C, respectively.
Accordingly, a primary object of the present invention is to provide a simple synchronizing apparatus and method in which two or more signals (e.g., picture signals including a luminance signal and a color signal), one of which is delayed, can be synchronized without employing a delay circuit.